An image processing apparatus includes: a category area dividing unit that divides each image constituting the time-series images of an object to be examined, which are captured in time series, into category areas including an examined area and an abnormal candidate area, the examined area showing the object to be examined, the abnormal candidate area being possibly an abnormal area showing an abnormal site of the object to be examined; an optical flow calculator that calculates optical flows of the examined area and the abnormal candidate area from images constituting the time-series images; and an abnormal area detector that compares the optical flow of the examined area and the optical flow of the abnormal candidate area, and detects the abnormal candidate area as the abnormal area according to the result of the comparison.